A couple more words on this - some manufacturers actually test t/s with a larger signal than a woofer tester do but you will never see published specs of a hot driver.
Jeff Bagby, who usually knows what he's talking about has been saying that as a driver heats up the t/s specs shift in complementary ways so that the box size requirement stays the same as the driver heats up. He's the only one that I've seen mention that and my experience does NOT agree with this. I've measured a driver cold and hot and the hot driver definitely wanted a bigger box.
And one more note before I head out to work.
Can you run your ported box model through the Filter Wizard and put up a screenshot of your displacement at the current high pass filter settings?
Then set it properly in the Wizard so it doesn't exceed xmax and let me know what the proper setting is?
Then reset your hpf in your system and listen to it with a variety of tracks and let me know if it makes an appreciable difference?
EDIT - it might be hard to tell a difference if you can't switch back and forth on the fly. But if it's a big enough difference you will notice it. You might not like the new setting. In my car there was a HUGE difference between the lowest setting (15 hz) and the proper setting (somewhere around 30). My car was way too loud anyway so I just left it at the lowest setting which was usually safe for any volume level I could bear to listen to. I hated the proper hpf setting.
It's best to do this sooner than later because it could influence your desired F3 for this new sub.
I'm curious about all this and forgot to mention it at the time because I can't keep up with you.
Can you run your ported box model through the Filter Wizard and put up a screenshot of your displacement at the current high pass filter settings?
Then set it properly in the Wizard so it doesn't exceed xmax and let me know what the proper setting is?
Then reset your hpf in your system and listen to it with a variety of tracks and let me know if it makes an appreciable difference?
EDIT - it might be hard to tell a difference if you can't switch back and forth on the fly. But if it's a big enough difference you will notice it. You might not like the new setting. In my car there was a HUGE difference between the lowest setting (15 hz) and the proper setting (somewhere around 30). My car was way too loud anyway so I just left it at the lowest setting which was usually safe for any volume level I could bear to listen to. I hated the proper hpf setting.
It's best to do this sooner than later because it could influence your desired F3 for this new sub.
I'm curious about all this and forgot to mention it at the time because I can't keep up with you.
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Unfortunately I have no way to test t/s 🙁 That is probably a very good idea. I don't know if I'm going to get there with the momentum I am feeling toward simply building the box.
By bigger box do you mean larger volume or horn length, or both? I could increase the height by an inch or two easily to be on the safe side...
I'll run the vented enclosure filter wizard and see what I get. I can absolutely change that on the fly with minidsp (built a usb connection into the box for it). It allows you to connect to the device during use and make adjustments
By bigger box do you mean larger volume or horn length, or both? I could increase the height by an inch or two easily to be on the safe side...
I'll run the vented enclosure filter wizard and see what I get. I can absolutely change that on the fly with minidsp (built a usb connection into the box for it). It allows you to connect to the device during use and make adjustments
Here is a comparison between the tapped horn sim above and the existing vented box with HPF applied to limit excursion
I got carried away
Very nice design - what cad software are you using? I am not sure if HR captures this, but when you do a side-by-side mouth on a horn you get additional bass extension because of the reflection symmetry. I did not know HR works on a mac...
Okay I was able to do that for the tapped horn, but I don't get the same menu options when simming the ported box- the diaphragm pressure option seems to disappear when in ported box mode.
I'm inclined to think these drivers are very strong. I know this is no way to quantify the strength of a driver, but these 15HP1060's are among the beefiest of 15s I've ever seen. The cone itself is extremely thick and I've never seen a bigger neo magnet structure with my own eyes. A world of difference from my 3015LF's.
You're going to need more bracing, particularly on that panel to the back, which looks completely unbraced at the moment.
Eh??
Looks like a misquote. Perhaps he was referring to effect of break-in, not the effect of heat.
To do a decent approximate simulation of the possible effects of heat on the response curve, just select the "Power" view, select the "Driver" option, then bump Re up a bit in the Loudspeaker Wizard. This will sim the effect of heat increasing the voice-coil's resistance (yes, yes, Fs may be slightly impacted because the spider is hotter too, but I'm going to go out on a limb here and say the biggest contributing factor to any response change due to a hot driver is the change in electrical damping (Qe) caused by the increase in the voice coil's resistance).
There's a jig you can make with $2 worth of parts that you probably have lying around anyway, a couple 3.5mm jack ends and a resistor that will worth with LIMP (ARTA) to test t/s if your soundcard plays nice with it. There's a list of approved soundcards and even if yours isn't on the list it might work. Or you can buy a woofer tester. Or don't worry about it.
By bigger box I mean same tuning but more undamped. Your sim that you commented on was almost ruler flat across the passband except for the spikes. Your current sim looks better, a bit of bumps is a good thing.
Yeah I forgot there's an extra step for ported boxes.
From input screen click Calculate.
Go to Acoustical Power - Tools - Output - Port
Go to Diaphragm Displacement - Tools - Diaphragm Pressure - Total
Danley uses good drivers with strong cones too, but like I said he doesn't go much above 2:1 compression ratio. Will your drivers survive? Almost certainly. Will it be ideal? Maybe not.
Yup.
I still recommend the other layout with throat in the middle, that will solve most of the bracing issue by itself. This layout is just going to waste a bunch of space putting in a bunch of bracing that the other layout doesn't need (at least it doesn't need as much).
Magnets get weaker too, when you heat them up.
It is an especially strong effect in Iron-Neo's and Cobalt Samarium's (I know, I've never seen a speaker with SmCo magnets).
Dave
It is an especially strong effect in Iron-Neo's and Cobalt Samarium's (I know, I've never seen a speaker with SmCo magnets).
Dave
No, not a misquote, he's mentioned this a few times. I hope you appreciate this, searching for anything on that forum is a hellish experience. I had to use google advanced search and a lot of luck to find this:
The first bold sentence is what he was responding to. This isn't the best quote but it's what I could find. IIRC he went into detail in other posts about the complimentary shifting of t/s parameters so the required box doesn't change as the driver heats up. That quote is from here - How important is sensitivity? [Archive] - Techtalk Speaker Building, Audio, Video Discussion Forum
Now it's entirely possible that his definition of "within reason" is a lot different than mine. I'm not very reasonable when it comes to driver abuse.
Not just Re and Fs are affected, everything changes. I've measured hot and cold drivers and every spec changes. The suspension is looser because it's been moving, the coil is hot so all the electrical parameters are different, looking at the two measurements looks like a completely different driver.
Anyway, adding a bit of Re is how I was told to estimate the effect of a hot driver too, and it's usually how I do it these days since I don't have an impedance tester at the moment (and also usually don't own the drivers I'm simulating).
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I thought I remembered reading about this somewhere. Jbell also recommended that when running stadiumhorns next to each other, you keep the mouths next to each other.
I'm using hornresp within Crossover for mac, which is a graphical WINE environment. I dislike VM software, and most speaker apps are basic enough that they run perfectly in Crossover... bassbox pro as well.
For modeling I am using Cinema4D, and for CAD I am using the Rhino beta for mac which is free (and I've used both for years).
Overall I am very pleased with it, I see no need to use a PC... Maybe if I was an akabak I would run a VM for it.
I don't see an issue using a slight bit more 0.5" bracing for the back wall, it will add maybe 1-2lbs. Plus I am really sold on the look of the center brace in the mouth. Adding another similar one in the back shouldn't be an issue 🙂
Guy- I have a PreSonus Firestudio Mobile audio interface, maybe that has the necessary specs to handle what you mention? I am extremely handy when it comes to diy electronics and I have plenty of spare resistors & audio jacks laying around. Thanks for the tip!
I can get away increasing the box height by about 2.5", but I think I am going to try to translate that volume into more horn length if possible to reach a lower F3, sacrificing some efficiency is okay with me.
3.71:1 compression in the previously modeled TH looks strangely identical to the vented box
Makes me want to go even a bit higher on compression to save space and increase exp flare, but not too much... Maybe 4:1 or 4.2:1. Thoughts?
shadydave- I did notice after the 2hr run the vented system had this past Saturday there was a noticeable amount of fatigue by the end, could have also been my battery voltage dropping that contributed to that as well...
More about Bagby -
Actually now that I read the thread he briefly posts 3 or 4 times about this issue in that thread. He makes his position pretty clear.
I was surprised, his evaluation of the situation does not match mine.
Actually now that I read the thread he briefly posts 3 or 4 times about this issue in that thread. He makes his position pretty clear.
I was surprised, his evaluation of the situation does not match mine.
That's because it is the same. When I did a quick sim to verify the steps to do this it did the same thing for me, it showed the tapped horn that I had previously simulated. I thought I did something wrong so I reran the sim and went through the steps again and got a more realistic result. The ported box sim won't look anything like that, it should look more like this.
An externally hosted image should be here but it was not working when we last tested it.
I wouldn't but you can do whatever you like. This is a small design, compromises are going to have to be made and you have to decide where to make them. Squeeze the flare? Raise F3? It's up to you.
Weight isn't the issue, extra bracing costs space. You are wanting to fight for more space by lowering compression ratio, but then adding a couple lbs of bracing where you wouldn't need it with a different layout.
But again it's up to you.
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Yeah, it looks like you both were talking about two different things.
1. The parameters will change dynamically as excursion increases. The "large-signal parameters" he's referring are likely those to be expected at a more significant excursion level than what you'd expect with a small signal. And yes, maybe these types of changes "balance out".
However..
2. For the type of listening you'd expect in a living room, it's hardly likely that there will be any appreciable change in the driver's temperature while the system is being used because most people don't run their living room systems "to the ragged edge of destruction". This is of course not the same for PA, and there WILL likely be a change in Re (and other attributes previously mentioned) of the drivers. These changes will not "balance out" to provide the same results predicted by t/s parameter modelling. If there did, there would be no compression at higher average power levels, right? 🙂.
The main issue I am seeing is that the centered pattern is much harder to fold given my space requirements. Maybe it will be easier now that I've sqeezed the flare a bit... I'll give it another go, why the heck not. I do like that one a lot too if it would fit.
The symmetrical layout uses almost twice the plywood for a given path length compared to both drivers using the same pat, reducing available internal space and increasing weight.